1. Field
This invention relates generally to structures and devices including an anchored array of carbon nanotubes (CNT) that extend from a conductive composite for application as a current conductor and fully or part of the electrode for an electrochemical power device such as a battery, supercapacitor, fuel cell, or the like. Additionally, the invention also generally relates to methods of manufacture of the structures and devices described above.
2. Related Art
Electrochemical power devices described herein generally include devices that can: store electrical energy in chemical form and release it back in electrical form on demand (for example, a Li ion battery that is used in mobile phones; convert chemical energy into electrical energy (for example, a fuel cell that can use a chemical fuel such as hydrogen or methanol and convert it into electrical energy); and/or store electrical energy and release it on demand (for example, a supercapacitor).
While the mechanism of energy storage and conversion maybe different in these devices, one common aspect of all these devices is the need for current conductors and/or electrodes. Each device typically has two electrodes, an anode, through which current flows into the device, and a cathode, through which current flows out of the device. Sometimes, a current collector, typically a metal such as copper or aluminum, is used in addition to or as part of an electrode for improved electrical conduction.
Carbon nanotubes (CNT) are generally known to have excellent electrical conductivity, thermal conductivity, mechanical strength, and chemical resistance. Although CNT have been observed over half a century ago, recent predictions of the remarkable physical properties of CNT sparked widespread interest in this material and CNT have been touted as the new material of the 21st century. CNT have been studied widely and various groups have proposed potential applications for this material in composites for higher strength and thermal conductivity, nano-probes and nano-pipettes for biomedical applications such as targeted drug delivery, field emission devices such as light emitting diodes, energy generation devices such as solar cells, nanoscale contact probes, nanoscale semiconductor device applications, electrodes for electrochemical energy devices such batteries, fuel cells, supercapacitors, and so on.
In the area for electrochemical energy devices, for example, CNT based structures have been suggested as potential candidates for electrodes for batteries, fuel cells, and supercapacitors. In particular, in the Lithium Ion battery field, there are several examples of utilizing CNT in electrodes. U.S. Pat. No. 6,709,471 discloses a CNT-Boron Nitride battery, which includes a structure utilizing the walls of the CNT as electrodes with Boron Nitride as an intermediate dielectric layer. Further, U.S. Pat. No. 5,879,836 describes using carbon fibrils as lithium intercalation sites in an electrode. Yet another example includes U.S. Pat. No. 7,442,284, which describes the use of an array of CNT coated with a conductive polymer as an electrode for various devices including energy storage devices.
In the field of fuel cells, U.S. Pat. No. 7,585,584 describes utilizing CNT grown on a carbon substrate with catalyst particles deposited on the CNT. Further, in the field of supercapacitors, U.S. Pat. Nos. 6,665,169 and 6,205,016, describe utilizing carbon nanofibers as electrodes to increase performance.
In addition to CNT, CNT based composites, which generally include conductive materials embedded with CNT, have been studied in an effort take advantage of the many desirable properties of CNT (see, e.g., “Carbon Nanotube Composites” Author: Harris P. J. F. International Materials Reviews, Volume 49, Number 1, February 2004, pp. 31-43(13)). Various CNT based composites and various techniques are known. For example, CNT-polymer composites are typically made by dissolving pre-treated CNT dispersed in a solution containing the polymer and controlled evaporation of the solvents (see, e.g., M. S. P. Shaffer and A. H. Windle: Adv. Mater., 1999, 11, 937-941; and D. E. Hill, Y. Lin, A. M. Rao, L. F. Allard and Y.-P. Sun: Macromolecules, 2002, 35, 9466-9471.), while CNT-ceramic composites are typically made by hot pressing ceramic powders with CNT (see, e.g., E. Flahaut, A. Peigney, C. Laurent, C. Marliere, F. Chastel and A. Rousset: Acta Mater., 2000, 48, 3803-3812; and A. Peigney, E. Flahaut, C. Laurent, F. Chastel and A. Rousset, Chem. Phys. Lett., 2002, 352, 20-25) and CNT-metal composites have been produced using hot drawing of CNT and metal powder (see, e.g., T. Kuzumaki, K. Miyazawa, H. Ichinose and K. Ito: J. Mater. Res., 1998, 13, 2445-2449), electroless plating (see, e.g., W. X. Chen, J. P. Tu, L. Y. Wang, H. Y. Gan, Z. D. Xu and X. B. Zhang: Carbon, 2003, 41, 215-222), co-electroplating a metal and CNT (see, e.g., “Effects of Additives on Cu-MWCNT Composite Plating Films,” Susumu Arai, Takashi Saito, and Morinobu Endo, Journal of The Electrochemical Society, 157 (3) D127-D134 (2010); and “Fibrous Nanocarbon Metal Composite and Method for Manufacturing the same,” U.S. patent application Ser. No. 11/257,742, filed Oct. 25, 2005) and electroplating a metal onto an array of CNT (see, e.g., “Nanoengineered thermal materials based on carbon nanotube array composites,” U.S. Pat. No. 7,273,095). All of the references cited in the present disclosure are incorporated by reference herein as if fully set forth in their entirety.